Shrinking Arctic Sea Ice Verges on New Record Low

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BOULDER, Colorado, August 28, 2008 (ENS) - Evidence that Earth's climate continues to heat up comes this week in the form of satellite data that shows the extent of Arctic sea ice this year has shrunk below the 2005 minimum to stand as the second-smallest since observations from space began 30 years ago.

Last summer, the extent of Arctic sea ice shrank to more than 30 percent below average, its smallest extent in the satellite record.

Each year, the Arctic Ocean experiences the formation and then melting of vast amounts of ice that floats on the sea surface. An area of ice the size of Europe melts away every summer reaching a minimum in September.

Because the extent of ice cover is usually at its lowest about mid-September, this year's minimum could still fall to set another record low, American and European scientists say.

This year the sea ice is melting more quickly than it did in 2005, say scientists at the National Snow and Ice Data Center in Boulder. "The most recent ice retreat reflects melting in the Chukchi Sea off the Alaskan coast and the East Siberian Seas off the coast of eastern Russia," they said in a statement Tuesday.

The latest satellite observations suggest that the Arctic could be mainly ice-free before 2040, Professor Heinrich Miller from the Alfred Wegener Institute in Bremerhaven, Germany said today.

In 2005, at its minimum point, Arctic sea ice extended over 2.05 million square miles (5.32 million square kilometers).

By comparison, Arctic sea ice extent on August 26 was smaller, measuring 2.03 million square miles.

Arctic sea ice reflects sunlight, keeping the polar regions cool and moderating the global climate. According to scientific measurements, Arctic sea ice has declined over at least the past 30 years, with the most extreme decline seen during the summer melt season.

These conclusions are confirmed by observations from the European Space Agency's Envisat satellite. The ESA said today in a statement, "Envisat observations from mid-August depict that a new record of low sea-ice coverage could be reached in a matter of weeks."

Scientists on the Wegener Institute's ice-breaking research vessel Polarstern also are studying Arctic sea ice by sailing from Iceland through the most direct route - the Northwest Passage, which is currently almost free of ice.

This is the second year in a row that the most direct route through the Northwest Passage has opened up. The indirect route, called the Amundsen Northwest Passage, has been passable for almost a month, Miller said..

"Polarstern will circumnavigate the whole Arctic Ocean and exit through the Northeast Passage," Miller said. Polarstern is expected to reach Bremerhaven again on October 19.

"The polar regions, especially the Arctic, are very sensitive indicators of climate change," Miller said. "The UN’s Intergovernmental Panel on Climate Change has shown that these regions are highly vulnerable to rising temperatures and predicted that the Arctic would be virtually ice-free in the summer months by 2070.

"Other scientists claim it could become ice-free as early as 2040," he said. "Latest satellite observations suggest that the Arctic could be mainly ice-free even earlier."

In 2009, ESA plans to launch another satellite, CryoSat-2, that will orbit the Earth for three years, gathering further evidence on the rates at which ice thickness and cover are diminishing.

The rate of climate warming over the land masses of northern Alaska, Canada, and Russia could more than triple during periods of rapid sea ice loss, according to a study by scientists at the National Center for Atmospheric Research and the National Snow and Ice Data Center.

The findings, released in June, raise concerns about the thawing of permafrost, or permanently frozen soil.

"Our study suggests that, if sea-ice continues to contract rapidly over the next several years, Arctic land warming and permafrost thaw are likely to accelerate," said lead author David Lawrence of NCAR.

Arctic soils are believed to hold 30 percent or more of all the carbon stored in soils worldwide, and thawing permafrost may release additional greenhouse gases that would further accelerate global warming.

Lawrence noted that from August to October last year, air temperatures over land in the western Arctic were unusually warm, reaching more than four degrees Fahrenheit (two degrees Celsius) above the 1978-2006 average, and he wondered whether this warming was related to the loss of sea ice.

Using sophisticated climate change simulations, Lawrence and his team found that during episodes of rapid sea ice loss, the rate of Arctic land warming is 3.5 times greater than the average 21st century warming rates predicted in global climate models.

While this warming is greatest over the ocean, the simulations suggest that it can penetrate as far as 900 miles inland, especially in autumn.

Lawrence and his team concluded that a decade of rapid sea ice loss could see autumn temperatures warm by as much as nine degrees F (five degrees C) along the Arctic coasts of Russia, Alaska, and Canada.

The study sheds light on how interconnected the Arctic system is, says co-author Andrew Slater, a scientist at the National Snow and Ice Data Center. "The loss of sea ice can trigger widespread changes that would be felt across the region."

Recent warming has degraded large sections of permafrost, with pockets of soil collapsing as the ice within it melts. The results include buckled highways, destabilized houses, and "drunken forests" of trees that lean at wild angles, Lawrence said.

"An important unresolved question is how the delicate balance of life in the Arctic will respond to such a rapid warming," he said. "Will we see, for example, accelerated coastal erosion, or increased methane emissions, or faster shrub encroachment into tundra regions if sea ice continues to retreat rapidly?"